I'm trying to create an extended partition. In GParted, I shrunk the size of the existing partition and now want to create a new EXTENDED partition in the free, unallocated space. GParted only lets me create a PRIMARY partition. What am I doing wrong here?

Here's what I've got right now:

You can actually ignore the flag for the swap as "boot." That was me just messing around trying to get it to work. I've removed that flag. Not sure how the question of boot affects all of this...maybe it factors in somehow.